Method for developing nuclear fuel and its application
Devices for generating heat and electric energy by nuclear fission reactions. The device includes a cylindrical tube, and a drain tube disposed inside having openings along its length for receiving drain fluid. The device also includes means forming the fuel layer disposed within the operative portion of the tube. The fuel layer generates fission products and has a thickness smaller than the fission product range. Drain fluid passes over the surfaces of the fuel layer, collects the fission products for discharge therefrom. The fuel hetero-structure is formed from the fuel layer, an insulating material and a liquid. The insulating material has a repetitive structure that includes at least three layers and interacts with the fission products to generate electricity. One of the layers generates electrons showers that are converted into heat or electricity.
This application claims the benefit of U.S. Provisional Application No. 60/748,489, filed on Dec. 7, 2005, which is hereby incorporated by reference in its entirety.
BACKGROUNDDuring the past few decades, nuclear reactors have been developed as a solution to reduce the greenhouse effect due to burning of carbon-based fuels, such as coal, petroleum, natural gas and oil. Conventional nuclear fuel is generated by the process of sintering uranium dioxide (UO2) powder into pellets. These pellets are covered by cladding material and form a reaction channel. In general, a nuclear reactor has a cooling system that surrounds each reaction channel and takes the fission-produced heat energy out. This heat energy is transferred through a series of heat exchangers to a turbine connected to an electro-mechanical generator, where the total exchange efficiency of a typical nuclear reactor is less than 40%.
As depicted in
As discussed above, the major damages to conventional fuel pellets during operation originate from the mismatch of temperature distribution 220 (
To generate electricity, gas turbines operating at high gas temperature may be used. Alternatively, electricity can be harvested directly by use of a direct conversion method similar to the beta-voltaic method. The direct electricity generation, also called direct conversion method, has been developed since 1940. As reactors using the direct conversion technique are not heated by fission reaction and remain cold, even cryogenic, they can be used in various types of generators, such as mobile and/or modular power generators. The major difficulty in enhancing the operational efficiency of conventional direct conversion circuits stems from spatial incompatibility between the locations where the nuclear power is present and the conversion is performed. Thus, there is a need for a new conversion circuit that may reduce the spatial incompatibility and enhance the conversion efficiency.
SUMMARYAccording to one embodiment, a nuclear fuel assembly for a nuclear reactor includes: a generally cylindrical elongated tube having an inlet end and a closed opposite end defining an operative portion; a drain tube disposed within the elongated tube and extending from the inlet end through the operative portion to the closed end, the drain tube having openings along its length for receiving drain fluid; and means forming at least one fuel layer disposed within the operative portion of the elongated tube. The fuel layer is operative to generate fission products by fission reactions. Drain fluid caused to enter the operative portion through the inlet end passes over the surfaces of the fuel layer, captures the fission products and passes through the openings and thence along the drain tube for discharge therefrom.
According to another embodiment, a device for converting fission energy into electrical energy includes: a fuel layer for generating fission products by fission reactions; one or more CIci layer units stacked on the fuel layer, each CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer; and an electrical circuit coupled to the high and low electron density layers and operative to harvest electrical energy. The fission products generate electron showers in the fuel layer and the high electron density layer while the low electron density layer absorbs the electron showers.
According to yet another embodiment, a tile for converting particle and radiation energy into electrical energy includes: a first layer including one or more CIci layer units, each CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer, the first layer being operative to absorb a first portion of particles and radiations moving toward the surface thereof and to convert the energy of the first portion into electrical energy; a second layer formed over the first layer and including one or more CIci layer units and being operative to absorb a second portion of particles and radiations that have passed through the first layer and to convert the second portion into electrical energy; and a third layer formed over the second layer and including one or more CIci layer units and operative to capture neutrons that have passed through the first and second layers and to convert the energy of neutrons into electrical energy.
According to still another embodiment, a device for converting fusion energy into electrical energy includes: a chamber having a wall comprised of at least one CIci layer unit, the CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer, the wall having at least two holes facing each other; two storage ring colliders for respectively sending fusion particle beams into the chamber through the two holes, the two beams traveling in directions opposite to each other; and means for focusing the two beams onto a collision spot in the chamber so that the two beams make fusion reactions at the spot. The wall absorbs fusion products generated by the fusion reactions and converts the energy of fusion products into electrical energy.
According to a further embodiment, a nuclear pellet includes: a generally cylindrical cladding layer; a metal grid covering a first transverse cross section of the cladding layer; a lower support covering a second transverse cross section of the cladding layer; and nuclear fuel grains filling a space bounded by the cladding layer, metal grid and lower support and capable of generating transmutation reactions. The liquid flows through the cladding layer and thereby washes the grains and carries recoils generated by the transmutation reactions.
BRIEF DESCRIPTION OF THE DRAWINGS
The bi-material fuel may be made from other suitable pairs of materials insofar as the pairs have the similar characteristics as discussed in conjunction with
The insulator 502 operates as an electrical, a chemical, or a molecular separator for separating the generator 501 from the absorber 503 and is associated with either the generator 501 or the absorber 503. The insulator 502 may be in the form of a layer, molecules, or clusters. The insulator 502 assures the separation properties enhancing the material interface properties by faceting or coating. In the case where both the generator 501 and absorber 503 are liquids, the insulator 502 may be used to provide the mechanical stability. The insulator 502 is invisible to the moving entities, such as fission products, electrons, recoils and other particles including molecules, ions, photons (X, gamma), and cosmic rays.
The absorber 503 is formed of a material, a material compound, chemical combinations, or alloys and is designed to stop the particles produced by the generator 501. For the fission products, knock-on electrons, and recoils, the absorber 503 functions as a stopping device and its material is mainly selected based on the capability of performing the deceleration process without major structural and chemical changes in time. The materials may be liquids, liquid metals, salts, solids, or gases. For the knock-on electrons, the absorber material is selected such that the absorber is able to stop the electrons without generating other electrons in interaction with the generator agent. The material may be conductor or superconductor with low electronic emissivity. Preferably, the material has low electronic density and is in the form of solid, liquid, or plasma. Conventional low-electron density materials may be included in the absorber 503. For recoils, the absorber 503 is formed of material that has different chemical properties than the recoils and stabilizes the recoils so as to make them easy to collect, concentrate, and separate from the absorber material.
Upon selection of materials for the three components 501, 502, 503, a linear dimension, called “effective length” can be defined by weighting the effects of interest, wherein the effects of interest occurs within the effective length. In the case of generator 501, the generated objects are not self-absorbed within a reasonable range, “effective length of the generator (EfLG) 507,” with or without the maximization of the desired phenomenon: “the generation”. The curve 505 represents the number of absorbed particle per unit length. As can be noticed, the generator 501 absorbs a small fraction of particles. As such, in practice, EflG 507 is determined considering the self-absorption of particles as well as other technological conditions, such as maximization of generation, mechanical stability, chemical stability, self-repairing, clusterization, etc. In the case of the absorber 503, the desired phenomenon is the maximization of the absorption of the product generated by the generator 501 with the optimization of other effects, such as minimization of the production of particles, maximization of stability, minimization of structural damage, maximization of current transport, heat, particles, etc. The curve 506 represents the total number of particles stopped as a function of distance from a surface of the generator 501. The effective length of the absorber (EfAL) 510 represents a characteristic length for producing absorption to a desired extent. Due to the fact that calculations are performed considering the whole assembly of materials, EfAL 510 of the absorber 503 becomes the difference between the absorption effective length EfLA 508 and EfLG 507 and the insulator thickness EfGI 509, truncated at a technological value. The technological value refers to a dimension that can be technologically obtained and is stable in time.
In practice, the optimization is performed considering a sequence of optimization conditions and the effective lengths are calculated iteratively. The effective lengths are, in the case of fission products, in the micrometric domain while, in the case of electrons and recoils, the effective lengths are in the nanometric domain. In the case where both fission products and electrons/recoils are considered simultaneously, the effective lengths are in the nano-micro domain and a hybrid structure is obtained.
The drain fluid 630 is a liquid metal that does not chemically interact with the fuel 622. There are several materials for the drain liquid, such as Na, K, NaK, Al, Zr, ZrNb, Pb, Bi, PbBi, etc. The type of drain liquid determines the temperature range where the reactor operates. The exact calculations for a nuclear reactor application require the knowledge of the neutron properties in all materials, material purity, mixing ratios, shapes, etc. for reaching the criticality in the reactor structure.
The insulating layer 626 increases the passivity of the fuel towards the drain liquid 630, allows the operational temperature to increase, and also reduces the rim effect due to the burnup. For structural reasons, the fuel 622 is tightly secured to lateral supports, such as cladding, i.e., both sides 601, 609 of the core 624 as well as the porous walls 602 and 610 are secured to the lateral supports (not shown in
During the operation of the reactor, the fission reaction occurs in various locations 604, 607, for instance. The spheres 605, 606 represent the ranges that fission products can travel through the fuel 622 and drain liquid 630. The radii of the spheres 605, 606 depend on the material type, concentrations, type and energy of fission product, etc. The fission product paths, which are represented by arrows 612, depend on the energy and pulse conservation at the fission point 607. The stopping process takes about few pico-seconds, and at the end of the range, some other type of energy release may happen (like beta disintegration of the fission product, being accompanied by neutrino and gamma release).
The dimension of fuel 622 in the y-direction is shorter than the stopping range so that most of the heat, lattice damage, and beta release occur in the drain liquid 630. Assuming that the fuel and drain liquid have a same stopping power and the distribution of the range locus has a spherical shape (605, 606), it is found that only a portion of the fission products flying within the solid angle 608 can escape the fuel 622 and decelerate to rest in the liquid 630. So the drain efficiency of the planar structure is about 50%.
A plot 628 represents a distribution of the predicted fission product concentration in an arbitrary unit (horizontal axis) along the vertical axis. The F, T letters denominate the fuel thickness and the total thickness of a pair of fuel-drain liquid layers, respectively. The thickness of the fuel is set to about 80-90% of the particle range in the fuel, where the range is about 14 microns for conventional urania fuel. The stopping in PbBi (LBE—Lead Bismuth Eutectic) drain liquid is even harder. So, as an example, a modulus of 10-10 microns of Urania-LBE may be used in the fuel assembly shown in
The fuel may be fabricated by selective excitation vapor deposition in one of the following shapes: 1) planar shape of a condenser structure with vertical stability connections, and 2) conical shape when the object is tilted and spins. The fuel structure may be: 1) low temperature structure when the fuel is made from metallic compounds like U—Pb; Pu—Ga/PbBi, AmU/Pb, 2) medium temperature structure when the fuel is made from Urania, Thoria, Plutonia in tungsten lattices and the LBE drain fluid is encapsulated in stainless steel cladding for NaK or LBE cooling, or 3) high temperature structure when the fuel is made from ceramics of UCWTi and self sustained in a WCTi cladding with Zircalloy drain liquid and He cooling.
For the reactor fuel channel design, the positions and directions of the fuel structure need to be considered. As an example, for LBE drain liquid, due to high static pressures, a horizontal and low tilted structure or a short structure is recommended, while for NaK drain liquid, orientation may not be important because the static pressure drop is relatively small.
As depicted in
The fuel 701 may be manufactured by controlled vapor deposition of solid drain fuel on micromeshes, then by annealing and compressing the drain fuel to be removed or by electro-deposition of metallic structures. For high temperature reactors, tungsten or titan carbide based structures may be used. The fuel 701 may be formed of a mixture of metal and carbides with structural material. As in the case of
The fuel has vertical stabilization points 810 to prevent the webs from skidding under the flow of the drain fluid 814. The drain fluid 814 may pass through the porous walls 810, 811, 821. In this structure, the escape factor is increased up to 90%, but is strictly dependent on the dimensions of the fuel and meshes. For diluted fuels made from high-enriched uranium (HEU), plutonium, or americium, and embedded in the drain fluid, the escape efficiency may increase up to 99%.
The tungsten mesh stand up to 3200° C. and, if the fuel beads are chemically coated by C implantation or carbon plasma discharge, the entire structure may stand over 2000° C. The fission products are generated at locations 804, 807, 813 and their penetration ranges are represented by spheres 805, 809, 812, wherein the spheres mainly end in the drain fluid 814. The interface 803 between the fuel bead 801 and the drain liquid 814 increases the structural stability. It is noted that only six beads are shown in
During operation, the fission act occurs in various locations 902, 906 and the fuel nucleus splits generating 2-4 neutrons and two middle mass fission nuclei 907 that travel through the fuel into the drain fluid 932. The fission products decelerate to stop at the end of the penetration range, creating loci or spheres of probabilities 903. When stopped by the drain liquid 932, a fission product produces a regional dislocation to generate a micro pressure shock wave, and may or may not react with the drain liquid to create a suspension. The fuel to drain liquid interface needs to be specially treated to prevent the suspension from clogging. The prevention may be obtained by deposition of delta layers that create a compact structure in the fuel. An example is the action of Gd in Pu lattices. PuC or PuGdC coated with a gold delta layer repels the fission products towards the drain liquid. The fuel structure shown in
The radial levers 1107, 1113 are attached to and actuated by external levels 1105. From the mechanical point of view, the radial levers 1107, 1113 form discontinuous surfaces and anchor the fuel disks 1110 to allow radial diameter modification, cone angle sharpening and twisting the disks into helical shapes, thereby to assure the maximum fuel compression with minimal friction between the wall of the pellet tube 1100 and the external lever 1105 and radial levers 1107, 1113. There are other compressible structures, such as squares, hexagons, or other polygons, which assure the compression and shape transformation of the fuel pellet during operation. Drawing out the entire reaction channel and using the other end to unlock the fuel, by removing all and refilling with appropriate material, may prevent the embitterment and incompatibility of the fuel structure. The fuel case 1114 and the fuel pellet 1111 may have a cylindrical shape, and the small pellets having cylindrical shape are simply added in the cladding tube and kept in contact by the compression force made by the lid devices mounted at the extremes of the cladding tube 1114. In this configuration the porous tube continuously contacts the cladding by guiding fins 1109. The cladding tube 1114 may have a variable cross section to form a frustum. In this case the pellet tube 1100 is discontinuous and together with the guiding fin 1109 creates a longitudinal lever 1111, and assures the pellet's external surface stability.
The reactor fuel tube 1250 includes: a cylindrical channel wall 1215, preferably double-channeled; permeable lids 1213, 1220; central tube 1211 having a porous wall and forming a passageway for drain fluid that is injected through one end 1219; and a stack of fuel meshes or conical disks 1252 that are similar to the disks 1110 shown in
The fuel meshes or conical disks 1252 are loaded into the tube 1250 by temporarily removing the lid 1213. Typically, the fuel meshes 1252 may be taken out of the tube 1250 at the end of a fuel cycle, wherein the fuel meshes 1252 are pushed from the base to the tip of the tube during the cycle. At the start of the fuel cycle, the fuel meshes 1252 may be located near a dotted region 1214 and has no poison therearound. As the fuel reactivity is high in the region 1214, a high volume of drain liquid between the fuel meshes is needed, i.e., fuel density is lowered in the region 1214. At the end of the cycle, the fuel meshes 1252 may be located near a dotted region 1218. Each fuel mesh near the region 1218 may contain less than ½ of the initial fuel; nevertheless, it is desirable for the fuel mesh to maintain good reactivity until being removed from the reactor.
The fuel tube 1250 behaves like a variable density tube for compensating the criticality loss due to the fuel burnup. At the initial stage of fuel cycle, the fuel has a high criticality. For example, a 1 Gwe reactor consumes fuel about 2 Kg/day. Per year, it will consume about 750 Kg of pure fuel. In about 10 years of operation it will consume about 7.5 tons. Thus, to compensate for the criticality loss due to the fuel burnup, the initial mass has to be greater than 15 tons. The correlated action of the absorption rods and channel profile will allow the fuel, when coming out of the reactor, to lose 60-80% of the pure fuel.
The angle 1246 is continuously varied from the entry 1214 to the end of cycle 1218.
As depicted in
As depicted in
As describe in conjunction with
The plot 1400 shows the ratio Vfluid/filler as a function of the ratio L/R as the ratio varies from 2 to 20. As can be noticed, the ratio Vfluid/Vfiller varies by a factor of 2000 while the distance ratio changes by a factor of 10. This means that in the case of the lowest dilution at which the criticality needs be compensated, a variation of the ratio L/D from 15 to 2 yields a change of Vfluid/Vfiller by a factor of 1000, covering a wide range of concentration and thereby enhancing the burning ratio up to 99%. As an example, consider the case of Uranium Dioxide (urania) for which the beads diameter may be around 10 micrometers. The initial startup distance L may be 300 micrometers, while the ending distance may be 25 micrometers. During this entire compression path 99.9% of the uranium has been consumed. In reality, a burning factor of about 90% or higher might be achieved considering other safety factors applied to this fuel. Compared to conventional burning factors, the fuel usage is increased by a factor of 10.
The inset diagram 1404 shows the chosen fuel cells. Other elementary cells may be chosen to assure better compression factors. Also a combination of 1 part UC in 2 parts of UO2 may be chosen to have a consumable cell eliminating CO2, while the fission occurs, bringing a positive criticality variation due to the modification of the total neutron cross sections as a consequence of the burning, to compensate for the partial fission product retention in the bead.
As discussed in conjunction with
The effects of insulator on the thermal conductivity and thermal stress amelioration can be noticed. The insulator material with a role in providing adhesive forces also constitutes a higher conductive shell, with lower expansion coefficient than the material covered thereby. As such, the insulator will push the inside material as a superficial membrane, with a role in providing mechanical consistency and stability. Moreover, because the heat energy is deposited on the portion adjacent the insulator, the temperature inside the bead is homogenized. By this mechanism, the destructive temperature gradient inside the fuel may be reduced and the temperature is mainly constant inside the fuel and maintained at equal or slightly higher than the liquid interface temperature. In
The energy is produced by fission reaction, which depends on the neutron flux. The neutron flux inside the structure may have a linear dependence on the input neutrons, up to the sub-critical configuration where the neutron flux amplification occurs. At criticality, the neutron flux becomes independent of the input, or amplification becomes very high. Thus, external neutron generation is no longer required to maintain the reaction and it becomes self-sustainable up to supra-critical domain where the chain reaction develops exponentially into uncontrolled domain (explosion). The neutrons may be produced by electron accelerators, where electron accelerators also called betatrons, (with an extraction energy from 20 to 100 MeV/n), or by ion accelerators that discharge protons or heavy ions into spallation targets (at an extraction energy of 50 MeV/n) or by specific neutron release reactions in light nuclei (Be, Li). The annihilation energy of positron may also be used to generate neutrons by gamma-n reactions using giant resonance in nuclei. The combination of a fission discharge chamber at the center of a sub-critical structure with photo-fusion, or plasma discharge can be also used. Alternatively, an accelerator storage ring collider based or a sono-fusion neutron generator can be used.
As depicted, the reactor 1650 includes the reactor blanket 1600 that offers a high albedo, minimizes the neutron leakage, and absorbs neutrons that otherwise may escape from the reactor. The blanket for high temperature reactors has to be cooler than the center, so the cooling fluid 1601 is introduced from the border. Due to the fact that the actual waste treatment tubes are very difficult to control and require unpleasant reactivity variations and multiple chemical reprocessing stages, specialized pipes 1602 for burning poisons and breeding are used to control permanent reactivity and waste treatment. The drain fluid flows at the speed of few millimeters per hour. That is because, even after the fission products decelerate to stop mainly by the drain liquid, they have still excited nuclei and can further disintegrate by the beta decay process. After about a week, the average life-time becomes longer and the specific radioactivity falls by a factor of 10. During this period, for many reasons, it is better to contain the fission product inside the reactor and use the same shielding and heat removal system. When delivered to a separation unit, the drain liquid is still radioactive, so this unit 1603 has to be very simple and reliable. Alternatively, a remote processing of the drain fluid may be done by use of a pair of clean and contaminated tanks.
The reactor 1650 may be operated in a sub-critical condition in conjunction with an external controllable means. This requires a way to produce a controllable neutron distribution inside the reactor by use of neutron generation cones 1604. The neutron generation cones use a betatron with high WCu targets for energetic bremsstrahlung gamma rays exciting (gamma, n) resonances in fissionable product, spallation source on W, Pb targets, or simply by using the photons generated by electron-positron annihilation. Each of the neutron generation cones 1604 generates driving neutron flux cone 1605 on the opposite side of the reactor, enabling sector 1614 control of the power level.
The reactor fuel zone 1606 has a thoroidal shape and includes fuel tubes 1612 that may be of the type described with reference to
Drain fluid flows around the tubes 1612 and proceeds towards a central system 1607. It is not a requirement to impose a certain direction on the flow. The reactor may incorporate the future neutron production possibility based on fusion in order to harvest the energy of the fusion and amplify it by fission. For this to be accomplished, the central core cooling and neutron processing zone (moderation; multiplication) 1608 contains both a cooling and fusion cavity 1619. The fission is mainly conceived for laser confinement and accelerator colliding beams. Alternatively, a magnetic confinement fusion capability may be added in the cavity. Hydrogen isotopes based fusion reactions may be used to deliver ions as fusion product and fast neutrons. The neutron energy is harvested by a central neutron generator converting shell 1609 and a system of tiles made by the same material is used to convert the energy of the fusion products into electricity. The neutron generation conic tubes 1604 are interlaced among the fuel rod tubes 1612 and control tubes 1613 that have neutron-absorption rods.
The control and generation of neutrons in sub-critical groups are done by assigning a generator 1604 to an opposite conic driving neutron flow domain 1614 and using the accelerators 1618 for driving the generators 1604. The central processing tubes 1617 for poison burning and breeding reduce the need for supplementary absorbers while improving the neutron usage balance.
The embodiment of the current power plant may have one or more of the following features. Firstly, the fuel without the compressibility feature to compensate for reactivity may be used in actual designs if the fuel pellets channels are modified accordingly. Secondly, controlling the poisons and actinides burning can be done in dedicated channels because of the burnup and reactivity issues. Thirdly, the fission products are to be continuously removed. Finally, the same power plant structure is good for breeding to generate high purity 239Pu, 233U at the level of calutron grade.
The reactor body 1700 contains the fuel tube 1701 with the drain liquid intake 1702. The nuclear fuel pellet 1703 contains a fuel mesh 1706 inside the pellet 1704, stabilized on a central tube 1707 for mechanic stability, and drain fluid inside the central tube 1707. The fuel handling area 1707 can be modified by adding lids for fuel handling and drain liquid circulation. The central rod and the exterior pipes 1702 and blanket have thermal resistors that bring the liquid metal into the liquid phase by maintaining the reactor's temperature over the melting point of the liquid metal.
The exit tube 1708 for cooling fluid is the same as conventional exit tubes. The cooling agent is PbBi (Eutectic)-LBE) liquid that gives mild or no reaction upon exposure to water. In Fast Breeder Reactors (FBR) structures, the LBE may be used as cooling agent too. The cooling fluid intake 1709 may have various designs. In the multitude of structures, the felt/mesh nuclear fuel may be used. In the hybrid structure, it will take the shape required by the design. For example, the intake 1709 has a vertical path in ultra high temperature reactor structure where the cooling is made by He gas, which powers a high temperature turbine, via a heat exchanger and circuit separator. In this case, the intake 1709 will adjust the flows such that the reactor's temperature field is maintained at constant level while the heat flow is to vary according the power requirements. The reactor bulk 1710, being a generic annotation, represents a multiplicity of the elements shown. The poison burning tube 1711 is designed to produce minimal amount of waste. The waste includes fission products (about 2 kg/day for each 1 Gwe/day) that are all radioactive and chemically hazardous. A dedicated extension to control the reactivity of the waste and byproducts is desired, or in the simplest case these fission products will be sealed in cooled lead and delivered to a specialized separation plant for reprocessing.
The poison control system has a poison intake system 1712 that is connected to the specialized poison separation unit 1723, which processes the poisons coming from the internal system 1722, analyses, and purifies the output from the poisons exhaust 1721 and sent through the neutron treatment channel 1713 in order to maintain the reactivity under control. This is a liquid circuit that controls poison concentrations.
It is noted that actinides are not poisonous waste; they are nuclear fuel. The fissile compounds are further burned, or delivered as newly created fuel, while the fertile may be further reprocessed or delivered as they are. The actinide management unit 1714 is divided into two specialized units: fertile transmutation 1716 to breed into fissile material and fertile actinides management unit 1717 that makes the local reactor actinide breeding policy drive the actinides to the actinide separator or purifier 1733 or to the actinide burning tube 1713. The reactor may be equipped with neutron generator tube 1715 if it is a type of accelerator driven to maintain a sub-critical structure.
An improvement of the current embodiment of the power plant is the distinct breeder management unit 1719 which accomplishes the fuel policy, by supplying via Uranium, Thorium supply unit 1718, the fertile isotopes for transmutation into fertile, and delivered correlated with the fissile actinides. In the current embodiment of the power plant reactor, the new breeding product enters in equilibrium with the initial fuel, creating various plutonium grades used for other applications. In this structure, the neutron-capture products travel together with the fission products and are separated later. The new breeding is using mainly the neutrons in after reflector blanket. The neutron capture product is delivered through the fissile material output unit 1720 that separates and purifies the fuel produced by breeding in the dedicated channels.
The electric power production system uses hot cooling agent that comes after a chain of heat exchangers in the turbine inlet 1728 of the gas turbine 1727, cools down and is returned to the reactor system by the turbine's exhaust 1726. The torque control unit 1725 controls the turbine's revolution speed for the electricity generator 1724. Used fuel may be transported by the drain liquid pushed by the drain fluid recycling pump 1731. The pump 1731 is connected to the fission products separation unit 1730, which may trigger an alarm of the fuel quality management unit 1729. The separated fission products exhaust 1732 drives the fission products and byproducts to the delivery unit 1734 for reprocessing and storage so that the products policy is met.
The “generator” layer with high electronic density remains polarized positively as it looses electrons, while the “absorber” layer with low electron density polarizes negatively as it stops the electrons. If the charges generated in these layers are not removed, an electrical potential builds up to the insulator's breakdown limit. If a suitable circuit 1918 is coupled to the plus (generator) and minus (absorber) layers by electrical connections 1916, an electrical energy can be directly harvested. To make effective CIci layers, it may be necessary to produce stable material interfaces, which can be realized by use of proper shapes.
The thickness of each layer may be in the nanometer range. For example, the thickness of a generator or high electron density, layer, if made of Gold (198Au), is about 30-55 nm, with an insulating layer made of SiO2 or Al2O3 and having a thickness of about 5 nm, and an absorber or low electron density layer made of Ti or Al and having a thickness of 15-25 nm. These layers may be repeatedly stacked in a thickness decreasing pattern to form a CIci structure that has an effective thickness of about 12 microns or more and terminates in PbBi liquid. The CIci structure may be manufactured by an ion beam assisted chemical vapor deposition technique, alternating the processes of gun deposition and ion etching. Another approach is to produce the generator layer from an actinide based superconductor that has both semiconductor properties and high electron density and is capable of generating electron showers and fission products, wherein the actinides and superconducting material are structurally interlaced.
The electronic cloud belonging to various atoms of the fuel is strongly perturbed by the fission product movement and associated radiation. The main process is ionization of the nuclei. While Fermi level is around few eV, the ionization energy drop is of about several KeV/Angstrom. Typically, an atom has a diameter of several angstroms. This simply means that the interaction of fission products with matter perturbs internal electrons in the lower orbits of the matter atoms and in turn removes the internal electrons from the atoms. As each electron has enough energy to share with the other electrons on its path, a nano avalanche, or equivalently electron shower, is created mainly in the direction of the flight path of fission product for impulse conservation reasons. Some other measurements show that when the energy of electrons reaches under a hundred eV, the path length basically becomes independent of the energy and becomes a measure of the Debye length. All the process of fission product stopping and electronic shower absorption is taking place in few pico-seconds, while the de-excitation and the equilibrium are reached in nano-seconds, being based on the return of the dislocated electrons back in structure under the action of the electric forces created by the polarization induced by the dislocations. The concept of direct conversion also relates to the interruption of the path of electron nano loops by use of a CIci structure. Generator, absorber and insulator materials have nanometric dimensions in order to be effective. For electrical polarization reasons, the network is insulated at element level, allowing the voltage to be accumulated as in a capacitor. The conversion efficiency is given by the ratio of the difference between the two avalanches over the total created charge. Typically, the insulator has a high breakdown margin to accommodate substantial accumulation of charges in the generator and absorber layers. The electrical potentials are in the domain of milli-Volts. In the interface between a cluster and an insulator, the quantum behavior may favor the exciton-phonon interaction, harvesting energy from all the possible modes and putting it in electric energy or making the polarization effects vanish. Moreover, the path is preferably short, because the volume distributed conduction is competing with the low resistance path conduction.
It is noted that the CIci layer can be applied to the fuel described in conjunction with
Fission products generated somewhere 2011 in the fissile fuel 2002 may have a flight path 2013 and generate an electronic avalanche 2014. Then the fission product penetrates the electrons absorber component 2004 it stops the previous electron shower that tunneled through the insulator 2005-2007 but, generates small avalanche 2016 or no-avalanche, and reaches the electron generator components 2006 to generate a strong avalanche 2014. For brevity, only one layer of Ae electron-absorber components and one layer of Ge electron generator components are shown in
The fuel spherule 2000 may be fabricated by ion beam assisted chemical vapor deposition on small targets. Starting from a tungsten, gold, Cu micro-mesh, the vapor deposition of fuel, such as Uranium or Plutonium, is made for a thickness of several microns. Over it, a several nanometers of dielectric material, such as carbon layer, is deposited by an electron beam, stimulating the formation of carbide layers. Then, a metallic layer is deposited followed by formation of insulation by reaction with oxygen, carbon, iodine and formation of dielectric material. Then, a stabilization element is added that reduces diffusion and layer degradation. A new conducting layer is deposited with a thickness of several nanometers, followed by formation of dielectric material and stabilization. A short electron beam or laser selected frequency is applied to anneal the layer, clusterize, and stabilize the structure.
A masking technique may be applied to make asymmetric depositions so that all the layers of one type are in contact with an end of the fissile bead. One type of material is in contact with an interior support conductor while the other is in contact with the exterior. An annealing process may be used to create a nano-wire like structure that will maintain the group conductivity. A several centimeter long wire with beads of fuel surrounded by the nano-wire like structure may be produced. The central nano-wire conductor is made of conducting material, such as Au, Ag, or Cu, has a diameter less than 1 micron and able to carry a current of several microamps. Then, a bead structured fissionable material having a radius of several microns is deposited, followed by a hundred of repetitive “CIci” layers connected to the center and the exterior. A very thin conductive exterior layer 2022 is deposited to cover the entire structure, wherein the conductive layer increases the electric contact with the drain liquid that serves as an electrode.
For brevity, only four spherules connected in parallel are shown in
The polarization of the electrodes 2108, 2110 in this super-capacitor structure is transmitted through the wires to a conversion unit 2112. To have a power level of 1 w for each cubic millimeter, an activity around 1 Curie is required, but the capability of existing materials for carrying current is limited. In such cases, cryogenic super-conductive structures can be considered. A practical delivery parameter can be 10 A at 10 mV, which corresponds to the limit of existing materials having a cross sectional area of 1 mm2. Supra-conductive technology opens the way to increase this limit by a factor of about 100. In these circumstances, activities up to 100 Ci/cmm are feasible, while operating with an efficient structure at liquid helium (LHe) temperatures. Pu based super-conductor alloys can make such structures operational at Liquid Nitrogen (LN) temperatures. For example, PuCoGa5 has a critical temperature of 18 K and there are many other high temperature supraconductors made from materials with low neutron interaction cross-section. For these application, a recovery mechanism may be conceived when parts of the reactor are raised to higher temperatures to eliminate the fission products and cure themselves by annealing.
On the surface of the fuel 2212, a faceted and stabilized insulating layer 2213 having a thickness of few nanometers is deposited. The insulating layer 2213 separates the fuel 2212 from a low-electron density layer 2214. The low-electron density layer 2214 has a role of electronic shower channeling on the surface's facets.
In order to completely close the electronic loops, a conductive shunt 2215, generated by ion implantation, is disposed. The conductive shunt 2215 is connected to all of the absorbent layers in the voxel 2202 so that the low-electron density layers are at the same electrical potential. The low electron density layer 2214 is surrounded by another insulating layer 2216 and a faceted delta layer 2217 that is formed of a high-electron density material. The layers 2213, 2214, 2216, and 2217 form a CIci layer structure. Additional sets of CIci layers may be stacked on the outer surface of the delta layer 2217 until the total thickness of the CIci layers reaches about 90% of the fission product range. Another conductive shunt 2218, which is connected to generator layers, may be grounded. As the voxels 2202 may be immersed in drain liquid during operation, the outermost layer of the voxel 2202 may be formed of a conductive material to enhance the electrical conduction at the interface and stabilizes the voxel content in the drain liquid. Multiple fuel-beaded wires 2219 are connected to create a bunch of wires with a macroscopic dimension and to produce power extraction at the level of 1 W/mm3. It is noted that harvesting the energy of a single disintegration at 80% efficiency may generate an electrical current of 3.2 nA at 10 mV. The multiple-beaded wire 2219 is a super capacitor formed of material that is neutron flux compatible. The properties and structure of the fuel bead 2219 may be produced for all the shapes defined in
It is noted that the device includes only one matrix of cells 2304. However, other suitable number of matrices of cells can be located around the fuel, where each matrix extends in a radial direction.
Due to the fact that each electronic loop cannot be extended very long, the loop length extends with only few orders of magnitude. In normal ceramic fuel the electron micro-loop (electron path) is less than few microns long, in a medium with the resistivity of hundreds of Mohm-m. When this loop is cut by the conductive layers with resistivity of mili-Ohm*m their length may not exceed few meters because the electrons will have same chance of following the long exterior path or traveling back through the insulator (it is called the minimum action principle invented by Fermat) So, from micron long electronic loops in dielectric, the new loops through normal conductors can be about ten millimeter long only. As such, it is beneficial to connect voxels in a pyramidal structure. To harvest electrical energy in nano-wire structured devices, many wires are connected in parallel and assembled in a bunch, wherein the wires are compacted into a structure immersed in drain fluid. The presence of the drain fluid as conductive layer is not a requirement. However, if the drain fluid is missing, an equivalent conductor has to be installed.
The central conductor 2404 is connected to the optional condenser unit 2405 and to a MEMS switch device 2406 that continuously alternates the polarity of current flowing out of the condenser unit 2405 so as to create an alternating current at a pair of electrodes 2407, 2408. The MEMS switch 2406 is controlled by a synchronization signal 2412 received from a central unit, and delivers alternating current through the switch's conductors 2407, 2408 into a micro-ferrite transformer 2409. The transformer 2409 raises the voltage level by at least 100 times, from millivolts to several volts, before the current is delivered to the conductors 2410, 2411. The current at the electrodes 2414 is also used by a centralized control system to diagnose the reactivity level and, in conjunction with the measured temperature of the voxels, to control the voxel's operation quality.
The voxel elements in
The second level transformer summation units 2508 sum outputs from the units 2501 and send the summed energy to the third level transformer unit 2512, closing a new current loop 2503. The third level transformer summation unit 2512 receives its power through conductor 2509 and may send its output current through a conductor 2514 to a unit at a higher level, where the output current may have tens to hundred of volts at few amps. It also closes the current loop 2517. A converter cascade may be used to transform 1-10 mV at the mm3 level into 100-1000V, several KA per reactor module at m3 level, giving powers in MW range. It is noted that other suitable number of units 2501, 2508 may be used without deviating from the spirit of the present teachings.
The second reactor structure 2609 is based on the novel principle of accelerator-driven reactivity control to synthesize the grid's frequency and phasing. The structure 2609 includes a reactor's structure 2610 that surrounds the reactor core 2611 having neutron generation area, where the accelerator's beam 2612 induces controlled neutron flux. The reactor 2611 is similar to the reactor described in conjunction with
The third reactor unit 2618 includes a reactor sector core 2620 having three sectors 2621. The sectors 2621 are hit separately by the accelerator beam and induce neutron flux 2622. The accelerator beam 2623, coming from an accelerator 2624, changes its impact location continuously, making a nonuniform and variable neutron flux. The accelerator 2624 is controlled by a feedback control loop 2625 to adjust the reactivity, such as reactor voltage 2617 applied to the tri-phased transformer 2626, and thereby to match the power grids needs. The transformer 2626 sends its output to the grid 2630 via a high voltage cable 2629. The reactor 2620 is similar to the reactor of
A fusion reaction may generate an alpha particle or a triton, called fusion product (He ion) 2706, with energy less than 6 MeV and/or neutrons 2707 with energies less than 15 MeV. The penetration range of the ion is short; typically, the ions stop in the first and second converters 2705, 2704, while the neutrons may travel into the third converter 2703. Due to the large collisional cross section of the actinide content in the layer 2703, the neutrons induce fissions and recoils. The neutrons resulted from a fission reaction 2708 may reach the shield 2701 and thence are reflected at a location 2709, or absorbed by the shield as a location 2710 due to the blanket's high neutron scattering cross-section.
The structure of planar tiles for energy harvesting in space may differ from the hetero-structure used in fission and fusion reactors having another MEMS connector because the voxels, if included in the planar tiles for space application, may be damaged by high-speed dust particles. A space vehicle payload carries protective shields that operate at cryogenic temperature environments and, at the same time, are exposed to high temperatures due to the energy transformation via amorphization in their thermal shield tiles.
As depicted, the shield 2812 has three layers 2822, 2823, 2824 that may have the same structures and functions as the layers 2705, 2704, 2703 in
The fusion products, such as He atoms, fly towards the inner surface of the blanket 2902 as indicated by an arrow 2910. The kinetic energy of fusion products is converted into current by the blanket 2902, where the harvest current 2911 is sent to the shuttle storage or grid. A portion of fusion products, such as He, flying in the most effective solid angle or cone 2913 exits through a hole 2914 formed in the blanket 2902 and is subsequently driven by a magnetic channel 2912. The fusion products exiting the channel 2912 are jettisoned from the space vehicle, which imparts thrust to the vehicle and thereby propel the vehicle in the space.
Depending on the type of particles interacting in fusion reaction or annihilation, the jet propulsion channel is used or not. When electron-positron annihilation is used, the energy-generating device 2902 is used in the entire surrounding sphere to generate electric current by absorbing the 511 KeV gamma rays.
The device 2902 uses hydrogen and lithium isotopes to produce Helium and energy. Some of the hydrogen isotopes react to release high-energy neutrons, as in the case of deuterium-tritium (D-T) reaction. The most easily harvested energy is the kinetic energy of He atoms, while neutrons carry over 50% of the fission energy. To harvest the neutron's energy, a fissile or a high collision cross section material/lattice is preferred. The deuterium-lithium reaction can be used in a hot accelerator structure to prevent Li deposition.
The vehicle also includes multiple shields 3012 that are similar to the shield 2812 in
The nuclear reactors described in conjunction with
The grains 3403, made from depleted uranium, Thorium, etc., are contained in the space between the metal grid 3402 and a lower support 3404. The pellet 3400 ends with a connection termination that can be coupled to an input 3401 of another identical pellet. At the bottom of the pellet 3405, the drain liquid exits the pellet as indicated by an arrow 3407 to a purification unit.
The mechanical stability, the grains is obtained by using bigger PM (particle magnitude) grains 3414 near the metallic foil 3411 and smaller grains 3415 in the center as shown in
The fuel breeding tube gets slightly warm from the incident neutron and the subsequent beta and gamma disintegrations whose energy is few thousand times lower than that in the fission requiring slight cooling system. Its role is to produce controlled nuclear transmutation of the 238-Uranium and 232-Thorium that do not burn in the reactor but are highly abundant in the ore into the highly fissile 239-Plutonium and 233-Uranium extending the planet's nuclear fuel resources by more than 150 times. The advantage of this structure over the actual breeding technology consists in the fact that after the first capture reaction the compound nucleus is removed from the reactor hot zone into separator area and the unwanted reactions of neutron capture driving to 240-Plutonium, 234-Uranium are avoided, giving an extra pure isotope, easy to separate.
While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.
Claims
1. A nuclear fuel assembly for a nuclear reactor, comprising:
- a generally cylindrical elongated tube having an inlet end and a closed opposite end defining an operative portion;
- a drain tube disposed within said elongated tube and extending from said inlet end through said operative portion to said closed end, said drain tube having openings along its length for receiving drain fluid; and
- means forming at least one fuel layer disposed within said operative portion of said elongated tube, said fuel layer being operative to generate fission products by fission reactions;
- whereby drain fluid caused to enter said operative portion through said inlet end passes over the surfaces of said fuel layer, captures the fission products and passes through said openings and thence along the drain tube for discharge therefrom.
2. A nuclear fuel assembly as recited in claim 1, wherein said fuel layer includes a plurality of separated disks stacked along the axial direction of the drain tube and configured to circumscribe the drain tube.
3. A nuclear fuel assembly as recited in claim 1, wherein said fuel layer has a substantially conical shape in a spiral configuration and extends along at least a substantial portion of the operative portion.
4. A nuclear fuel assembly as recited in claim 1, wherein said fuel layer includes a plurality of rectangular plates, each plate having one side aligned along the axial direction of the drain tube.
5. A nuclear fuel assembly as recited in claim 2, wherein the cross-sectional diameter of the cylindrical elongated tube decreases as an axial distance from the inlet increases.
6. A nuclear fuel assembly as recited in claim 5, further including one or more radial levers for pushing the disks along the axial direction toward the inlet end thereby compensating for a loss of reactivity due to a fuel burnup process.
7. A nuclear fuel assembly as recited in claim 2, wherein the thickness of each said disk is less than a flight range, said flight range being a distance that the fission products can move in a fuel formed of the fuel layer.
8. A nuclear fuel assembly as recited in claim 7, wherein each said disk includes a fuel film coated with at least one CIci layer unit and wherein the CIci layer unit includes a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer.
9. A nuclear fuel assembly as recited in claim 2, wherein the disk is formed of one or more sub-layers, each sub-layer including a two dimensional mesh made of conducting wires and fuel beads located in knots of the mesh.
10. A nuclear fuel assembly as recited in claim 9, wherein each fuel bead is coated with at least one CIci layer unit and wherein the CIci layer unit includes a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer.
11. A nuclear fuel assembly as recited in claim 2, wherein the disk is formed of one or more sub-layers, each sub-layer including a three dimensional mesh made of conducting wires and fuel beads located in knots of the mesh.
12. A nuclear fuel assembly as recited in claim 11, wherein each fuel bead is coated with at least one CIci layer unit and wherein the CIci layer unit includes a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer.
13. A device for converting fission energy into electrical energy, comprising:
- a fuel layer for generating fission products by fission reactions;
- one or more CIci layer units stacked on the fuel layer, each said CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer; and
- an electrical circuit coupled to the high and low electron density layers and operative to harvest electrical energy,
- wherein the fission products generate electron showers in the fuel layer and the high electron density layer and wherein the low electron density layer absorbs the electron showers.
14. A tile for converting particle and radiation energy into electrical energy, comprising:
- a first layer including one or more CIci layer units, each said CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer, the first layer being operative to absorb a first portion of particles and radiations moving toward the surface thereof and to convert the energy of the first portion into electrical energy;
- a second layer formed over the first layer and including one or more CIci layer units and being operative to absorb a second portion of particles and radiations that have passed through the first layer and to convert the second portion into electrical energy; and
- a third layer formed over the second layer and including one or more CIci layer units and operative to capture neutrons that have passed through the first and second layers and to convert the energy of neutrons into electrical energy.
15. A tile as recited in claim 14, further comprising a blanket formed over the third layer and provides bio-protection and damps radiations hitting the surface thereof.
16. A tile as recited in claim 15, wherein the third layer includes actinides and wherein the neutrons and actinides generate fission reactions to amplify the energy of neutrons.
17. A tile as recited in claim 14, wherein the tile operates under a cryogenic environment, further comprising one or more lateral conductor-and-cooling separators surrounding the side edges of the first, second and third layers.
18. A device for converting fusion energy into electrical energy, comprising:
- a chamber having a wall comprised of at least one CIci layer unit, the CIci layer unit including a high electron density layer, a first insulating layer, a low electron density layer, and a second insulating layer, the wall having at least two holes facing each other;
- two storage ring colliders for respectively sending fusion particle beams into the chamber through the two holes, the two beams traveling in directions opposite to each other; and
- means for focusing the two beams onto a collision spot in the chamber so that the two beams make fusion reactions at the spot,
- wherein the wall absorbs fusion products generated by the fusion reactions and converts the energy of fusion products into electrical energy.
19. A device as recited in claim 18, wherein the wall has a third hole and the fusion products passing through the third hole are jettisoned from the device to impart propulsion thrust to the device.
20. A nuclear pellet, comprising:
- a generally cylindrical cladding layer;
- a metal grid covering a first transverse cross section of the cladding layer;
- a lower support covering a second transverse cross section of the cladding layer; and
- nuclear fuel grains filling a space bounded by the cladding layer, metal grid and lower support and capable of generating transmutation reactions,
- wherein liquid flows through the cladding layer and thereby washes the grains and carries recoils generated by the transmutation reactions.
Type: Application
Filed: Nov 21, 2006
Publication Date: Jun 14, 2007
Inventor: Liviu Popa-Simil (Las Alamos, NM)
Application Number: 11/603,812
International Classification: G21C 3/00 (20060101);